Computing devices and communication networks can be utilized to exchange content and other information. In a common application, one computing device (such as a server computing device) can provide content to another computing device (such as a client computing device). The content may be provided with the intent to cause or provoke an action by the other computing device or a user of the other computing device. The content may be sent as an email, a web page, an interstitial page, a content item to be displayed on a web page, or the like.
In some scenarios, particular users or computing devices can be selected to receive new or changed content, while other users or computing devices can be selected to receive existing or unchanged content. Differences in how the sets of users interact with the provided content can then be analyzed to determine what effect, if any, the new or changed content has in comparison with the existing or unchanged content. For example, a server computing device may select, from a universe of available users, a subset or “control set” of users. The server computing device may also select a “treatment set” from the universe of available users. The control set and treatment set can be selected ahead of time, or users can be added to the respective subsets in response to requests for content. Content provided to users in the treatment set may be new, changed, or otherwise different versions of content provided to users in the control set. Responses or other user interactions with the provided content can be analyzed to determine whether the content provided to the treatment set users has provoked or otherwise resulted in different actions than the content provided to the control set users.